bug#68931: 30.0.50; Gnus byte-compilation error with (display . [not expire]) with git emacs

[Stefan Monnier]

> We could (and probably should) allow this for compatibility but perhaps it's
> time to at least start warning about it? It makes the quirky semantics of
> a Lisp-2 even quirkier.

I think it falls basically in the same category as ((lambda ..) ..),
indeed: we should accept it but emit a warning.


        Stefan